This invention is an improved electrical discharge-machining fixture that retains the electrode while minimizing variations in the position of an electrode within the fixture.
Electrical discharge machining (EDM) is a highly accurate method of drilling or machining metals. An electrode is attached to an EDM fixture for drilling or machining the metals. Because of the high accuracy, EDM is commonly used to drill airfoil cooling holes in the surface of turbine blades. In order to achieve accurate drilling the retaining fixture for the electrode must have a high degree of repeatability with minimal position variations for the electrode.
When using EDM to drill holes within turbine blades a stamped electrode comb is typically used. The comb has a relatively thin cross-section when compared to the width of the comb. The shape of the comb makes reliably positioning the electrode and retaining the electrode within the EDM fixture difficult. It is also desirable to be able to control the clamping force placed on the electrode by the retaining feature.
When using the currently known retention method a clamp retains and positions the electrode during the EDM operation by applying force to the electrode. External forces such as dielectric fluid flushing and movement of the machining axes during the EDM operation cause the electrode to release or move within the clamp.
An improved fixture for retaining an electrode that has minimal positional variations for the electrode and an adjustable retaining force that allows automated insertion and injection of the electrode for use in electrical discharge machining is needed.